U.S. patent application number 10/165128 was filed with the patent office on 2003-12-11 for mixed flow pump.
Invention is credited to McBride, Mark W..
Application Number | 20030228214 10/165128 |
Document ID | / |
Family ID | 26861130 |
Filed Date | 2003-12-11 |
United States Patent
Application |
20030228214 |
Kind Code |
A1 |
McBride, Mark W. |
December 11, 2003 |
MIXED FLOW PUMP
Abstract
The present invention relates to propulsion and hydraulic
systems having a co-axial design wherein the inlet section,
impeller section, and outlet section of a mixed flow pump system
all have a common centerline axis or axis of rotation. The mixed
flow pump system includes an outer casing and a central body
disposed co-axially within the outer casing. A pump impeller is
rotatably connected to the central body for imparting hydraulic
energy to the fluid flowing through the mixed flow pump system. The
mixed flow pump system may also include inlet flow conditioning
vanes for conditioning an inlet flow of fluid to the mixed flow
impeller for improving the cavitation performance and/or acoustic
performance of the pump module. Stator vanes are provided for
connecting the central body to the outer casing and to remove any
swirl velocity from the fluid flow exiting the mixed flow pump
impeller. The mixed flow pump system exhibits improved resistance
to cavitation due to the use of one or more of inlet flow
conditioning vanes and low RPM motors for rotating the mixed flow
pump impeller. The invention has applications in a variety of
applications, including propulsion and hydraulic applications. For
example, the invention may be used for the propulsion of marine
vehicles, such as submerged crafts, weapons and unmanned underwater
vehicles (UUVs) of various sizes and speed requirements. The mixed
flow pump may also be applied to non-marine applications such as
hydraulic applications, chemical distribution systems, and medical
devices.
Inventors: |
McBride, Mark W.;
(Bellefonte, PA) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
ONE LIBERTY PLACE, 46TH FLOOR
1650 MARKET STREET
PHILADELPHIA
PA
19103
US
|
Family ID: |
26861130 |
Appl. No.: |
10/165128 |
Filed: |
June 7, 2002 |
Current U.S.
Class: |
415/191 ;
415/192; 415/211.2 |
Current CPC
Class: |
B63H 11/08 20130101;
F04D 13/06 20130101; F04D 29/4273 20130101; B63H 23/24 20130101;
F04D 29/448 20130101; F04D 3/00 20130101 |
Class at
Publication: |
415/191 ;
415/192; 415/211.2 |
International
Class: |
F04D 029/54; F04D
029/54 |
Claims
What is claimed is:
1. A co-axial mixed flow pump comprising: an outer casing having a
longitudinal centerline axis; a central body aligned co-axially
within said outer casing along said longitudinal centerline axis;
an axial forward looking inlet formed along said longitudinal
centerline axis for receiving a flow of fluid; a mixed flow pump
having a rotating impeller mounted to a forward end of said central
body, said mixed flow pump impeller comprising: a hub; a plurality
of blades extending outward from said hub; and a plurality of flow
passages formed between adjacent blades, wherein said mixed flow
pump impeller rotates about said longitudinal centerline axis to
draw a flow of fluid into said mixed flow pump impeller through
said inlet and imparts energy to said fluid flow; an annular
passageway formed between said outer casing and said central body
on a downstream side of said mixed flow impeller for receiving said
fluid flow exiting said mixed flow impeller, said annular
passageway being aligned axially; a plurality of stator vanes
disposed between and connecting said outer casing and said central
body to condition said flow exiting said mixed flow pump impeller
to flow generally in the axial direction; an axial rearward looking
outlet formed along said longitudinal centerline axis for
discharging said flow of fluid from said mixed flow pump.
2. The mixed flow pump of claim 1, further comprising an inlet
section extending forward of said axial forward looking inlet, said
inlet section having a distal inlet opening at a forward end and a
length of inlet ducting connecting said inlet opening to said mixed
flow pump impeller.
3. The mixed flow pump of claim 2, wherein a forward portion of
said inlet section further comprises a flush inlet.
4. The mixed flow pump of claim 1, further comprising a plurality
of inlet flow conditioning vanes disposed in said inlet section to
condition a fluid flow flowing into said mixed flow pump impeller,
said inlet flow conditioning vanes connected at a first end to said
inlet ducting and extending into said inlet ducting to a distal
end.
5. The mixed flow pump of claim 4, wherein said inlet flow
conditioning vanes comprise straight vanes attached to and
extending radially inward from said outer casing to eliminate
distortions of said fluid flow.
6. The mixed flow pump of claim 4, wherein said inlet flow
conditioning vanes comprise curved vanes that are curved in the
same direction as the direction of impeller rotation to impart
swirl to the fluid flow entering said mixed flow pump impeller to
reduce the relative velocity of the fluid flow to decrease
cavitation and vibration noise.
7. The mixed flow pump of claim 4, wherein said inlet flow
conditioning vanes comprise curved vanes that are curved into a
direction of impeller rotation to impart swirl to the fluid flow
entering said impeller and to increase the relative velocity of the
fluid flow entering said mixed flow pump impeller to increase said
mixed flow pump head rise potential.
8. The mixed flow pump of claim 4, wherein said inflow conditioning
vanes extend radially into said inlet duct from said outer casing
in a radial direction toward said centerline axis of said outer
casing.
9. The mixed flow pump of claim 4, wherein said inlet flow
conditioning vanes are leaned in a circumferential direction as
said inlet flow conditioning vanes extend into said inlet duct.
10. The mixed flow pump of claim 4, further comprising a center
member extending axially forward from said central body into said
inlet section, wherein said inlet flow conditioning vanes are
extend radially outward from said center member and are attached to
said center member and said outer casing.
11. The mixed flow pump of claim 1, wherein said flow enters said
mixed flow pump impeller axially, flows through said mixed flow
impeller at an angle from said longitudinal centerline axis such
that a pressure developed by said mixed flow pump is developed
partly by centrifugal force and partly by a lift of said impeller
blades on said fluid, and discharges said mixed flow pump impeller
axially.
12. The mixed flow pump of claim 1, wherein said mixed flow pump
impeller blades further comprise an open blade construction having
a clearance gap formed between a distal end of said impeller blades
and said outer casing blades.
13. The mixed flow pump of claim 1, wherein said mixed flow pump
impeller blades further comprise a shrouded blade construction
having a shroud disposed at a distal end of each of said impeller
blades.
14. The mixed flow pump of claim 13, further comprising an embedded
shrouded blade construction, wherein said shrouds of said shrouded
impeller blades extend into and rotate within a groove in said
outer casing.
15. The mixed flow pump of claim 1, wherein said drive motor is
mounted axially rearward of said mixed flow impeller in said fluid
flow;
16. The mixed flow pump of claim 1, wherein said plurality of
stator vanes further comprise a curved wing-like shape for removing
swirl velocity from said fluid flow exiting said mixed flow
impeller and straightening said fluid flow to flow generally in the
axial direction.
17. The mixed flow pump of claim 16, wherein said stator vanes are
positioned at equal spacing around a circumference of said central
body.
18. The mixed flow pump of claim 1, further comprising an inlet
fairing that extends forward from a front end of said central body
toward said inlet section and provides smooth flow into said
impeller section and around said central body.
19. The mixed flow pump of claim 1, further comprising an outlet
fairing that extends rearward from a rear end of said central body
toward said outlet section, wherein said outlet fairing facilitates
a smooth flow as said flow exits said annular passageway.
20. The mixed flow pump of claim 1, further comprising an outlet
section having a forward end proximate said axial rearward looking
outlet and a length of outlet ducting connecting said annular
passageway to a discharge nozzle position in said outlet ducting
proximal a discharge opening for accelerating said fluid flow as
said fluid flow is discharged from said mixed flow pump.
21. A mixed flow pump for inputting hydraulic energy to a fluid
flowing therethrough comprising: an outer casing aligned axially
from a forward end to a rearward end, said outer casing comprising
an inlet section, an impeller section, and an outlet section; said
inlet section comprising: an axially aligned inlet opening at said
forward end; an axially aligned inlet duct having a generally
increasing cross-sectional area from a first end of said inlet duct
proximal said inlet opening to a second end of said inlet duct;
said impeller section connected to a downstream end of said inlet
section, said impeller section comprising: an axially aligned
impeller inlet connected to said second end of said inlet section;
an impeller sweep area having a generally increasing circular
cross-sectional area from said impeller inlet to an impeller
outlet; said outlet section connected to a downstream end of said
impeller section, said outlet section comprising: an axially
aligned inlet at a forward end of said outlet section connected to
said impeller outlet; an axially aligned outlet duct having a
generally decreasing cross-sectional area from said outlet section
inlet to a discharge; a central body disposed within and co-axial
with said outer casing, comprising: a stationary hub disposed
within said outlet section; a mixed flow pump impeller rotatably
mounted to a forward end of said hub and in said impeller section
for drawing a flow of fluid through said inlet duct and into said
mixed flow pump impeller; an annular passageway formed between said
central body and said outer casing and in said outlet section; a
stator blade assembly disposed between and connecting said central
body and said outer casing to provide structural support for said
central body, to remove any swirl velocity from said fluid flow
exiting said mixed flow pump impeller, and to convert kinetic
energy contained within the swirl velocity to pressure; and a drive
motor for rotating said mixed flow pump impeller.
22. The mixed flow pump of claim 21, further comprising inlet flow
conditioning vanes disposed in said inlet section and extending
into said inlet duct to condition said flow of fluid into said
mixed flow pump impeller.
23. The mixed flow pump of claim 22, wherein said inlet flow
conditioning vanes comprise curved vanes having a wing shape,
wherein said curved vanes are oriented to curve or turn in the same
direction as the direction of rotation of said mixed flow pump
impeller thereby reducing the relative velocity of said fluid flow
entering said mixed flow pump and reducing cavitation.
24. The mixed flow pump of claim 22, wherein said inlet flow
conditioning vanes comprise curved vanes having a wing shape,
wherein said curved vanes are oriented to curve or turn into the
direction of rotation of said mixed flow pump impeller thereby
increasing the relative velocity of said fluid flow entering said
mixed flow pump and increasing the head rise potential of said
mixed flow pump.
25. The mixed flow pump of claim 22, wherein said inlet flow
conditioning vanes extend radially into said inlet duct from said
outer casing toward said longitudinal centerline.
26. The mixed flow pump of claim 22, wherein said inlet flow
conditioning vanes are leaned in a circumferential direction as
they extend into said inlet duct.
27. A co-axial propulsion system comprising: an outer casing
comprising ducting having a longitudinal centerline, said ducting
for containing and guiding a fluid flow within said co-axial
propulsion system; a forward looking, axial inlet opening of said
outer casing centered about said longitudinal centerline for
receiving an axial flow of fluid from one of an internal fluid
system and an exterior fluid operating environment into an interior
of said co-axial propulsion system; a rearward looking, axial
outlet opening of said outer casing centered about said
longitudinal centerline for discharging an axial flow of fluid from
said interior of said coaxial propulsion system to one of said
internal fluid system and said exterior fluid operating
environment; wherein said ducting extends axially and connects said
inlet opening and said outlet opening; a central body disposed
co-axially within said outer casing; a mixed flow pump impeller
rotatably mounted to said central body and disposed coaxially about
said longitudinal centerline, wherein an axis of rotation of said
mixed flow pump impeller is co-axial with said longitudinal
centerline; an annular passageway defined between said outer casing
and said central body, said annular passageway being oriented
co-axially about said longitudinal centerline; a plurality of
stator vanes disposed co-axially about said longitudinal centerline
and extending radially between said outer casing and said central
body and extending through said annular passageway, said stator
vanes supporting said central body within said outer casing; and
wherein said stator vanes are configured to remove swirl velocity
from said fluid flow exiting said mixed flow impeller and
straightening said fluid flow to flow in an axial direction toward
said outlet opening.
28. The co-axial propulsion system of claim 27, wherein said
ducting further comprises inlet ducting formed between said inlet
opening and said impeller section and a plurality of inlet flow
conditioning vanes disposed in said inlet ducting for conditioning
said fluid flow to improve one or more of cavitation performance
and acoustic performance of said co-axial propulsion system.
29. The co-axial propulsion system of claim 27, further comprises
outlet ducting and a discharge nozzle for discharging said fluid
flow from said ducting to produce thrust, wherein said outlet
ducting is formed between said impeller section and said outlet
opening and wherein said plurality of stator vanes are disposed in
said outlet ducting.
30. A co-axial mixed flow pump system comprising: an outer casing
axially aligned about a centerline axis; a central body disposed
within said outer casing and aligned about said centerline axis; a
mixed flow pump rotatably mounted to a front end of said central
body and having an axis of rotation that is coincident with said
centerline axis; a plurality of stator vanes disposed between and
connecting said outer casing and said central body for removing
swirl velocity from a flow exiting said mixed flow pump and causing
said exiting flow to flow in an axial direction; an internal flow
passage defined by said outer casing, wherein said internal flow
passage further comprising: an axially inlet flow passage; an axial
inlet to said mixed flow pump; an axial discharge from said mixed
flow pump; an axially aligned annular flow passage defined between
said outer casing and said central body; and an axially aligned
outlet flow passage.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to the field of pumps, and
in particular, to improved mixed flow pumps for marine propulsion
and hydraulic applications.
BACKGROUND OF THE INVENTION
[0002] Conventional propulsors include numerous propeller, pumpjet
and water jet propulsion devices. These devices are typically
powered by an engine at a distance from the propulsor that is
connected by a shaft to the propulsor. The engine is typically
contained within a ship hull or pressure hull. Usually, a drive
shaft extends from the engine through the pressure hull to the
propeller, and bearings and a pressure seal are required to support
the shaft and provide water-tight integrity for the engine and
hull. These conventional propulsors contain motors that are located
inside the pressure hull and that are directly coupled to a
propeller that is located outside the pressure hull, with the flow
being an external, rather than an internal flow.
[0003] Some examples of prior art patents include U.S. Pat. Nos.
6,273,768; 6,267,632; 6,203,388; 6,168,485; and 3,939,794. For
example, U.S. Pat. No. 6,273,768 teaches that it is known to propel
a boat or other watercraft using a water jet apparatus mounted to
the hull, with the powerhead being placed inside (inboard) or
outside (outboard) the hull. The drive shaft of the water jet
apparatus is coupled to the output shaft of the motor. The impeller
is mounted on the drive shaft and installed in a housing, the
interior surface of which defines a water tunnel having a
convergent nozzle. The impeller is designed such that during motor
operation, the rotating impeller impels water rearward through the
water tunnel and out the convergent nozzle. The reaction force
propels the boat forward.
[0004] Conventional pumps include radial, axial, and mixed flow
pumps. In a typical axial flow pump, the radial distance of a fluid
particle from the pump centerline is constant from the pump inlet
to the pump outlet. In radial and mixed flow pumps, the radial
distance of a fluid particle from the pump centerline increases
along the length of the pump because these types of pumps typically
include a scroll or spiral type casing. Mixed flow pumps typically
have a discharge that is perpendicular to the axis of impeller
rotation.
[0005] A problem with conventional propulsors is that they
typically do not include any flow conditioning of the fluid flow
entering the pump impeller. For example, it may be desirable to
condition the inlet flow to affect pump performance in some way,
such as to reduce cavitation and improve acoustic performance of
the propulsor, increase the head rise potential of the pump, and
the like. Cavitation is generally undesired in conventional pumping
systems because cavitation results in lost thrust and acoustic
noise.
[0006] For example, U.S. Pat. No. 5,947,680 discloses
turbomachinery with variable angle inlet guide vanes and variable
angle diffuser vanes. However, the turbomachinery disclosed in U.S.
Pat. No. 5,947,680 only teaches straight inlet guide vanes that are
controlled in conjunction with the diffuser vanes to control the
angle of the vanes to suit an operating condition. Also, the
turbomachinery disclosed in U.S. Pat. No. 5,947,680 has variable
geometry vanes, not fixed geometry guide vanes. This design is to
adjust the performance to an optimum over a range of operating
points and does not, for example, provide superior performance at
one operating point. The device disclosed in U.S. Pat. No.
5,947,680 also includes a scroll discharge casing.
[0007] Another problem is flow conditioning of the outlet flow
exiting the pump impeller. For example, in radial and mixed flow
pumps, the rotating impeller imparts swirl to the flow as the
impeller rotates and this swirl velocity decreases the pump
performance.
[0008] Conventional propulsion pumps include various means for
straightening the fluid flow exiting the impeller. For example,
U.S. Pat. No. 4,427,338 discloses thrust control vanes for
waterets. The flow straightening vanes of the waterjet pump are
designed to produce a low-pressure area, and the downstream side of
the rotor drum is located inside the low-pressure area to eliminate
the need for an axial thrust control seal. Also, U.S. Pat. No.
4,929,200 discloses fixed flow-correction guide vanes positioned
downstream of a rotating impeller. A number of gas injection slots
are situated in the area of the trailing edges of the vanes for
introducing a volume of gas into the flow in the tail pipe section
of the pump in order to reduce internal drag resulting from
pressure exercised by the water against the pump casing. U.S. Pat.
No. 6,102,757 discloses a water jet propulsion device for a marine
vessel having guide vanes provided in the water passage in the rear
of the impeller for converting the guided swirl flows exiting the
impeller into straight flows. U.S. Pat. No. 5,417,547 discloses a
vaned diffuser for centrifugal and mixed flow pumps having two rows
of radially displaced vanes to more efficiently convert the kinetic
energy of the fluid flowing out from the impeller into static
pressure. In addition, U.S. Pat. No. 5,480,330 discloses using a
second impeller located rearward of a first impeller and which
serve to straighten the rearwardly directed water flow.
[0009] Therefore, a need exists for a mixed flow pump having
improved pump performance, reduced cavitation, and improved
acoustics performance. The need also exists for a co-axial mixed
flow pump.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a co-axial mixed flow
pump system having one or more of improved pump performance,
reduced caviatation, and reduced acoustic noise. The mixed flow
pump includes an outer casing having a longitudinal centerline axis
and a central body aligned co-axially within the outer casing along
the longitudinal centerline axis. An axial forward looking inlet is
formed along the longitudinal centerline axis for receiving a flow
of fluid. A mixed flow pump having an impeller rotatably mounted to
a forward end of the central body. The mixed flow impeller includes
a hub, a plurality of blades extending outward from the hub, and a
plurality of flow passages formed between adjacent blades. The
mixed flow pump impeller rotates about the longitudinal centerline
axis to draw a flow of fluid into the mixed flow impeller through
the inlet and imparts energy to the fluid flow. An annular
passageway is formed between the outer casing and the central body
on a downstream side of the mixed flow pump impeller for receiving
the fluid flow exiting the mixed flow impeller. The annular
passageway is aligned axially. A plurality of stator vanes are
disposed between and connecting the outer casing and the central
body to condition the flow exiting the mixed flow impeller to flow
generally in the axial direction. The mixed flow pump system also
includes an axial rearward looking outlet formed along the
longitudinal centerline axis for discharging the flow of fluid from
the mixed flow pump system.
[0011] According to one aspect of the invention, the mixed flow
pump, further includes an inlet section extending forward of the
axial forward looking inlet. The inlet section has a distal inlet
opening at a forward end and a length of inlet ducting connecting
the inlet opening to the mixed flow pump impeller. In an alternate
embodiment, the inlet section can further include a flush type
inlet upstream of the axially aligned inlet to the mixed flow
pump.
[0012] According to another aspect of the invention, the mixed flow
pump can further include a plurality of inlet flow conditioning
vanes disposed in the inlet section to condition a fluid flow
flowing into the mixed flow pump impeller. The inlet flow
conditioning vanes can be connected at a first end to the inlet
ducting and extending into the inlet ducting to a distal end. The
inlet flow conditioning vanes can comprise straight vanes attached
to and extending radially inward from the outer casing into the
fluid flow to eliminate any distortions in the fluid flow.
[0013] According to another aspect of the invention, the inlet flow
conditioning vanes can comprise curved vanes that are curved in the
same direction as the direction of impeller rotation to impart
swirl to the fluid flow entering the mixed flow pump impeller to
reduce the relative velocity of the fluid flow in order to decrease
cavitation and vibration noise. In an alternative embodiment, the
inlet flow conditioning vanes can comprise curved vanes that are
curved into a direction of impeller rotation to impart swirl to the
fluid flow entering the impeller and to increase the relative
velocity of the fluid flow entering the mixed flow pump impeller to
increase the mixed flow pump head rise potential.
[0014] In accordance with another aspect of the invention, the
inflow conditioning vanes extend radially into the inlet duct from
the outer casing in a radial direction toward the centerline axis
of the outer casing. Alternatively, the inlet flow conditioning
vanes can be leaned in a circumferential direction as the inlet
flow conditioning vanes extend into the inlet duct.
[0015] Furthermore, the mixed flow pump can further include a
center member extending axially forward from the central body into
the inlet section. In embodiments having a center member, the inlet
flow conditioning vanes can extend radially and be connected
between the center member and the outer casing.
[0016] In accordance with another aspect of the invention, fluid
flow enters the mixed flow pump impeller axially, flows through the
mixed flow pump impeller at an angle from the longitudinal
centerline axis such that a pressure developed by the mixed flow
pump impeller is developed partly by centrifugal force and partly
by a lift of the impeller blades on the fluid, and discharges the
mixed flow pump impeller axially.
[0017] According to another aspect of the invention, the mixed flow
pump impeller blades can include an open blade construction having
a clearance gap formed between a distal end of the impeller blades
and the outer casing blades. In an alternate embodiment, the mixed
flow pump impeller blades can include a shrouded blade construction
having a shroud disposed at a distal end of each of the impeller
blades. In yet another embodiment, the impeller blades can include
an embedded shrouded blade construction, wherein the shrouds of the
shrouded impeller blades extend into and rotate within a groove in
the outer casing.
[0018] Furthermore, the mixed flow pump can include a drive motor
that is mounted axially rearward of the mixed flow impeller in the
fluid flow. The motor can be housed the central body.
Alternatively, the motor can be mounted outside of the fluid flow
and a drive shaft, gears, bearings, etc. can connect the motor to
the pump impeller. In addition, a rim-drive type motor may be used
to drive the mixed flow pump impeller.
[0019] The plurality of stator vanes supporting the central body
within the outer casing can include a curved wing-like shape for
helping to remove swirl velocity from the fluid flow exiting the
mixed flow impeller and straightening the fluid flow to flow
generally in the axial direction. Preferably, the stator vanes are
positioned at equal spacing around a circumference of the central
body.
[0020] Moreover, the mixed flow pump can include one or more
fairings to help facilitate a smooth flow of fluid though the outer
casing and around the central body. For example, an inlet fairing
can be provided that extends forward from a front end of the
central body toward the inlet section and provides smooth flow into
the impeller section and around the central body. An outlet fairing
can be provided that extends rearward from a rear end of the
central body toward the outlet section in order to facilitate a
smooth flow as the flow exits the annular passageway.
[0021] In accordance with another aspect of the invention, the
mixed flow pump can further include an outlet section having a
forward end proximate the axial rearward looking outlet and a
length of outlet ducting connecting the annular passageway to a
discharge nozzle. The discharge nozzle can be positioned in the
outlet ducting proximal a discharge opening for accelerating the
fluid flow as the fluid flow is discharged from the mixed flow
pump.
[0022] In accordance with another embodiment within the scope of
the present invention, a mixed flow pump is provided for inputting
hydraulic energy to a fluid flowing therethrough. The mixed flow
pump includes an outer casing aligned axially from a forward end to
a rearward end. The outer casing includes an inlet section, an
impeller section, and an outlet section.
[0023] The inlet section includes an axially aligned inlet opening
at the forward end and an axially aligned inlet duct having a
generally increasing cross-sectional area from a first end of the
inlet duct proximal the inlet opening to a second end of the inlet
duct.
[0024] The impeller section is connected to a downstream end of the
inlet section. The impeller section includes an axially aligned
impeller inlet connected to the second end of the inlet section. An
impeller sweep area having a generally increasing circular
cross-sectional area is defined between the impeller inlet and an
impeller outlet.
[0025] The outlet section is connected to a downstream end of the
impeller section. The outlet section includes an axially aligned
inlet at a forward end of the outlet section connected to the
impeller outlet and an axially aligned outlet duct having a
generally decreasing cross-sectional area from the outlet section
inlet to a discharge opening.
[0026] According to another aspect of the invention, a central body
can be disposed within and co-axial with the outer casing. The
central body includes a stationary hub disposed within the outlet
section, a mixed flow pump impeller rotatably mounted to a forward
end of the hub and in the impeller section for drawing a flow of
fluid through the inlet duct and into the mixed flow pump impeller.
An annular passageway is formed between the central body and the
outer casing and in the outlet section. A stator blade assembly is
disposed between and connects the central body and the outer casing
to provide structural support for the central body, to remove any
swirl velocity from the fluid flow exiting the mixed flow pump
impeller, and to convert kinetic energy contained within the swirl
velocity to pressure.
[0027] A drive motor is provided for driving the impeller hub,
causing the impeller to rotate thereby adding hydraulic energy to
the fluid flowing through the mixed flow pump.
[0028] Inlet flow conditioning vanes can be disposed in the inlet
section to condition a flow of fluid into the mixed flow pump
impeller. The inlet flow conditioning vanes can include curved
vanes having a wing shape, wherein the curved vanes are oriented to
curve or turn in the same direction as the direction of rotation of
the mixed flow pump impeller, thereby reducing the relative
velocity of the fluid flow entering the mixed flow pump and
reducing cavitation, or the inlet flow conditioning vanes can curve
or turn into the direction of rotation of the mixed flow pump
impeller, thereby increasing the relative velocity of the fluid
flow entering the mixed flow pump and increasing the head rise
potential of the mixed flow pump.
[0029] The inlet flow conditioning vanes can extend radially into
the inlet duct from the outer casing toward the longitudinal
centerline. Alternatively, the inlet flow conditioning vanes can be
leaned in a circumferential direction as they extend into the inlet
duct.
[0030] In accordance with another embodiment of the present
invention, a co-axial propulsion system for use in propulsion and
hydraulic applications can be provided. The coaxial propulsion
system includes an outer casing for containing and guiding a fluid
flow within the co-axial propulsion system. The outer casing
includes ducting having a longitudinal centerline. The outer casing
has a forward looking, axial inlet opening centered about the
longitudinal centerline for receiving an axial flow of fluid from
one of an internal fluid system and an exterior fluid operating
environment into an interior of the co-axial propulsion system. The
outer casing also has a rearward looking, axial outlet opening
centered about the longitudinal centerline for discharging an axial
flow of fluid from the interior of the co-axial propulsion system
to one of the internal fluid system and the exterior fluid
operating environment. The ducting extends axially and connects the
inlet opening and the outlet opening.
[0031] A central body is disposed co-axially within the outer
casing, A mixed flow pump impeller is rotatably mounted to the
central body and disposed co-axially about the longitudinal
centerline, wherein an axis of rotation of the mixed flow pump
impeller is coaxial with the longitudinal centerline of the outer
casing. An annular passageway defined between the outer casing and
the central body, the annular passageway being oriented coaxially
about the longitudinal centerline.
[0032] A plurality of stator vanes are disposed co-axially the the
longitudinal centerline and extend radially between the outer
casing and the central body and also extend through the annular
passageway. The stator vanes support the central body within the
outer casing. The stator vanes are configured to remove swirl
velocity from the fluid flow exiting the mixed flow impeller and
straightening the fluid flow to flow in an axial direction toward
the outlet opening.
[0033] In accordance with another aspect of the invention, the
ducting further includes inlet ducting formed between the inlet
opening and the impeller section and a plurality of inlet flow
conditioning vanes disposed in the inlet ducting for conditioning a
fluid flow to improve one or more of cavitation performance and
acoustic performance of the coaxial propulsion system.
[0034] In accordance with another aspect of the invention, the
ducting further includes outlet ducting and a discharge nozzle for
discharging the fluid flow from the ducting to produce thrust,
wherein the outlet ducting is formed between the impeller section
and the outlet opening and wherein the plurality of stator vanes
are disposed in the outlet ducting.
[0035] In a further embodiment of the invention a co-axial mixed
flow pump system is provided for propulsion and hydraulic
applications. The co-axial mixed flow pump system includes an outer
casing axially aligned about a centerline axis, a central body
disposed within the outer casing and aligned about the centerline
axis. A mixed flow pump is rotatably mounted to a front end of the
central body and has an axis of rotation that is coincident with
the centerline axis. A plurality of stator vanes are disposed
between and connect the outer casing and the central body for
removing swirl velocity from a flow exiting the mixed flow pump and
causing the exiting flow to flow in an axial direction.
[0036] The co-axial mixed flow pump system also includes an
internal flow passage defined by the outer casing. The internal
flow passage further includes an axially inlet flow passage, an
axial inlet to the mixed flow pump, an axial discharge from the
mixed flow pump, an axially aligned annular flow passage defined
between the outer casing and the central body, and an axially
aligned outlet flow passage.
[0037] Additional features of the present invention are set forth
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 shows a cross sectional view of an exemplary mixed
flow pump;
[0039] FIG. 2 shows a partial sectional view of another exemplary
flow inlet to the mixed flow pump of FIG. 1;
[0040] FIG. 3 shows a detailed view of an exemplary embodiment
having straight inlet flow conditioning vanes;
[0041] FIG. 4A shows exemplary inlet flow conditioning vanes
extending radially inward from the inside circumference of the
outer casing;
[0042] FIG. 4B shows a detailed view of another exemplary
embodiment having inlet flow conditioning vanes that lean in the
circumferential direction;
[0043] FIG. 5 shows another exemplary embodiment having curved
inlet flow conditioning vanes and a center body;
[0044] FIG. 6A shows exemplary inlet flow conditioning vanes
extending radially inward from the inside circumference of the
outer casing to a center member;
[0045] FIG. 6B shows a detailed view of another exemplary
embodiment having inlet flow conditioning vanes that lean in the
circumferential direction as they extend between the outer casing
and the center member;
[0046] FIG. 7A shows a detailed view of an exemplary open impeller
blade that can be used with the mixed flow pump of FIG. 1;
[0047] FIG. 7B shows a detailed view of an exemplary shrouded
impeller blade that can be used with the mixed flow pump of FIG.
1;
[0048] FIG. 7C shows a detailed view of an exemplary embedded
shrouded impeller blade that can be used with the mixed flow pump
of FIG. 1; and
[0049] FIG. 8 shows a schematic view of an exemplary impeller and
drive motor of the mixed flow pump of FIG. 1 illustrating the flow
through the mixed flow pump.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] In the illustrated embodiments of the invention shown in
FIGS. 1-8, an improved mixed flow pump system I that provides
advantages in pump operational performance, and improvements in
cavitation and acoustic performance of the mixed flow pump system
1. As shown in the figures, the mixed flow pump system 1 includes
an outer casing 10 aligned axially about an axial centerline axis 2
and a central body 20 disposed within and aligned about the same
centerline axis 2 the outer casing 10. The mixed flow pump system 1
also includes a mixed flow pump 3 having an axis of rotation
aligned axially and that is coincident with the centerline axis 2.
Throughout the description, reference is made to a system inlet or
forward end 4a where the fluid enters the mixed flow pump from and
a system outlet or aft end 4b where the fluid exits the mixed flow
pump system 1.
[0051] FIG. 1 shows a cross sectional view of an exemplary mixed
flow pump system 1. As shown in FIG. 1, the outer casing 10
includes an internal flow passage comprising an optional axially
aligned inlet flow passage 6a, an axial inlet 6b to the mixed flow
pump 3, an axial discharge 6c from the mixed flow pump 3, an
axially aligned annular flow passage 6d defined between the outer
casing 10 and the central body 20, and an axially aligned outlet
flow passage 6e.
[0052] The mixed flow pump system 1 can receive a flow of fluid
from an internal system, such as a piping system, or an external
fluid operating enviromnent, such as a submersible vehicle
operating in the ocean.
[0053] As shown in FIG. 1, the outer casing 10 includes an inlet
section 11, an impeller section 12, and an outlet section 13. As
shown in the figures, the inlet section 11 includes a generally
increasing cross-section area for receiving a fluid flow into the
internal flow passage 6a-6e of the outer casing 10.
[0054] The impeller section 12 is located aft (e.g., down stream)
of the inlet section 11 and houses a mixed flow pump impeller 21
that rotates and adds hydraulic energy to a fluid as the fluid
flows through the mixed flow pump impeller 21. The impeller section
12 includes a generally increasing circular cross section that
extends over the impeller sweep area of the mixed flow impeller
21.
[0055] The outlet section 13 is located aft (e.g., down stream) of
the impeller section 12 and includes a generally decreasing cross
sectional area. As the flow exits the mixed flow impeller 21 it
passes through the annular passageway 6d between the outer casing
10 and the central body 20. As shown in FIG. 1, the annular flow
passage 6d includes a first or forward portion 8a having a
generally constant diameter and generally constant cross sectional
area and a second or after portion 8b having a generally decreasing
diameter and a generally increasing cross sectional area.
[0056] The impeller section 12 drives the fluid through the outlet
section 13 to a discharge nozzle 25 where the fluid is accelerated
and dispelled from the outer casing 10 to produce thrust.
[0057] Preferably, the outer casing 10 and the central body 20
include circular shaped ducting and a circular shaped body,
respectively. While the outer casing 10 in the impeller section 12
(e.g., the impeller sweep area) and rotating pump impeller 21 must
be circular, the rest of the outer casing 10 (including sections 11
and 13) and central body 20 are not limited to a circular shape.
For example, the inlet section and the outlet section need not be
circular in shape, and can include other suitable shapes.
[0058] In one preferred embodiment, the mixed flow pump system 1
includes a coaxial design and construction. Co-axial means that
there is a common centerline axis 2 for the various components of
the mixed flow pump propulsion system 1. Preferably, the axis of
rotation of the mixed flow pump impeller 21 is coincident with the
centerline axis 2. A single centerline axis 2 exists around which
the outer casing 10, central body 20, inlet section 11, impeller
section 12, and outlet section 13 are symmetrically disposed and
aligned (e.g., a common centerline axis 2 about which the system
inlet opening 4a, optional inlet ducting 15, optional inlet flow
conditioning vanes 40, mixed flow pump impeller 21, stator vanes
45, outlet ducting 24, and system outlet opening 4b are
symmetrically disposed or aligned). In addition, in a preferred
embodiment, a motor 50 for driving the mixed flow pump impeller 21
is also aligned about the same centerline axis 2 and is located in
the fluid stream.
[0059] The co-axial mixed flow pump 3 includes a substantial
straight-line flow in the axial direction into the mixed flow pump
3 from the pump inlet 6b and out of the pump outlet 6c. In
addition, the co-axial mixed flow pump system 1 preferably includes
co-axial flow from the system inlet 4a and through the inlet
section 11, through the outlet section 13 to the system outlet 4b,
with the impeller section 12 with the mixed flow pump 3 disposed in
between. Note that in the impeller section 12 there is flow in both
an axial and radial direction (e.g., "mixed flow").
[0060] This design results in a co-axial mixed flow pump system 1
having an axial centerline axis 2 of symmetry about which the
various components of the system are aligned and through which a
fluid flows substantially axially from the system inlet 4a to the
system outlet 4b. This is different than conventional mixed flow
pumps that typically have a scroll type casing (e.g., a spiral
snail shaped casing wherein the discharge flow is perpendicular to
the axis of rotation of the impeller).
[0061] In one embodiment, the co-axial mixed flow pump system 1 can
be located in a pod or modular propulsor having an internal flow of
fluid through the mixed flow pump outer casing 10. Vectored thrust
may be provided by a movable discharge nozzle, by moving the pod,
and the like. Inlet Section
[0062] Preferably, the mixed flow pump system 1 includes a forward
looking, axial inlet to the mixed flow pump 3 (e.g., an inlet that
is centered about the centerline axis 2 or axis of rotation of the
mixed flow pump impeller), as shown in FIG. 1. In one embodiment,
the mixed flow pump system 1 can received a flow from an internal
environment (e.g., wherein the pump is located in a piping system
and the piping before the pumps acts as the inlet per se and the
flow transits from the piping to the domain of the mixed flow
pump). In another embodiment, the inlet to the mixed flow pump can
receive fluid flow directly from an external fluid operating
environment directly into the mixed flow pump system 1 in the axial
direction (e.g., a vehicle operating in an external fluid
environment and receiving a flow from the fluid environment through
the pump inlet to the pump domain).
[0063] FIGS. 1 and 2 show exemplary inlet sections 11 of the mixed
flow pump system 1. FIG. 1 shows an embodiment of the mixed flow
pump system 1 having a forward looking, axial type inlet. FIG. 2
shows an embodiment of the mixed flow pump system 1 having a flush
type inlet as an alternative type of inlet that can be used with
the mixed flow pump system 1. Where a flush type inlet is used, at
least a portion of the inlet section 11 before the mixed flow pump
3 is aligned axially.
[0064] As shown, the inlet section 11 includes inlet ducting 15 for
containing and guiding a flow of fluid through the inlet section 11
to the impeller section 12. The inlet ducting 15 includes a first
end defining the system inlet opening 4a and a second end proximate
the pump inlet 6b. Preferably, the inlet ducting 15 has a generally
circular cross-section, although other shapes may be suitable. The
inlet ducting 15 may include a constant cross sectional area or a
generally increasing cross-sectional area from the first end to the
second end.
[0065] In embodiments having inlet ducting 15 having a generally
increasing cross-section, flow may be diffused by progressively
increasing the flow area to increase the pressure and decrease the
flow velocity, thereby improving cavitation performance in the
mixed flow pump system 1. This can be accomplished, for example, by
gradually increasing the diameter of a circular shaped outer casing
from a first end of the inlet section 11 at the inlet opening 4a to
a second end of the inlet section 11 connected to the impeller
section 12.
[0066] Inlet Flow Conditioning Vanes
[0067] FIGS. 1 through 5 show inlet flow conditioning vanes 40 in
the inlet section 11. As shown in FIG. 1, a plurality of inlet flow
conditioning vanes can be disposed around the circumference of the
inlet ducting 15 and extend inward into the fluid flow. Inlet flow
conditioning vanes 40 are used to condition the flow as it proceeds
to the impeller section 12. Conditioning means that the inward flow
of fluid to the mixed flow pump is influenced in some way. For
example, the flow conditioning vanes 40 can be used to eliminate
distortions, to impart swirl to the flow to either reduce the
relative velocity of the flow at the pump impeller inlet thereby
reducing cavitation and noise, to increase the relative velocity of
the flow to increase the pump energy input and efficiency, for
structural support, and the like. The inlet flow conditioning vanes
40 may also help to keep debris out of the pump impeller 21.
[0068] So, depending on the particular application, inlet flow
conditioning vanes 40 or a combination of flow conditioning vanes
40 can be used to improve the performance of the mixed flow pump
system 1. The improved performance can be in the area of
efficiency, cavitation, acoustics, etc. The inlet flow conditioning
vanes 40 can make the difference between a good mixed flow pump
system and an extremely good mixed flow pump system.
[0069] Preferably, the inlet flow conditioning vanes 40 are
disposed in the inlet section 11 and extend radially into the fluid
stream (e.g., along a line that is essentially a radial line from
the casing toward the center of the inlet ducting 15). As shown in
FIGS. 1, 2, 3, and 4A the inlet flow conditioning vanes are
attached at a first end 41 to the outer casing 10 and extend
radially into the fluid flow toward the center axis 2 of the pump
casing 10 to a second or distal end 42.
[0070] FIG. 4A shows four inlet flow conditioning vanes 40 having a
cantilever type design wherein the inlet flow conditioning vanes 40
extend inward from the inside circumference of the outer casing 10
along a radial line extending generally radially to the
longitudinal centerline axis 2 of the outer casing 10.
[0071] In another embodiment shown in FIG. 4B, the inlet flow
conditioning vanes 40 have lean or are leaned in a circumferential
direction to provide an acoustic benefit. As shown in FIG. 4B, four
inlet flow conditioning vanes 40 extending inward from the inside
circumference of the outer casing 10 and the individual inlet vanes
40 are leaned in the circumferential direction. The reason for this
is that fluid wakes from the inlet vanes 40 may interact with the
impeller blades 28 and the interaction of these wakes can be
minimized and the vibration that they cause can be reduced by
leaning the inlet vanes 40 in certain applications.
[0072] Preferably, the inlet flow conditioning vanes 40 are evenly
spaced around the circumference of the outer casing 10 and the flow
stream. For example, if three inlet flow conditioning vanes 40 are
used, then the inlet vanes 40 are preferably disposed 120 degrees
apart; if four inlet flow conditioning vanes 40 are used, then the
inlet vanes 40 are preferably disposed 90 degrees apart; etc.
[0073] The inlet flow conditioning vanes 40 may include a
cantilever design wherein the vanes span a portion of the inlet
duct 15 (e.g., extend into the fluid flow), or a beam-like design
wherein the inlet vanes 40 span the entire inlet duct 15, such as
in embodiments shown in FIG. 5 having a center member 43
arrangement. Although not required, the inlet flow conditioning
vanes 40 preferably extended a radial distance into the flow stream
substantially equal to the radius of the flow stream to maximize
the flow conditioning of the inlet flow stream.
[0074] FIG. 5 shows an alternative embodiment further including a
center member 43 or fairing coincident with the central body 20 and
the axis of rotation 2 of the pump impeller 21 and having the inlet
flow conditioning vanes 40 connected to the center member 43. The
center member 43 extends axially along the longitudinal centerline
axis 2 of the mixed flow pump 1 from the central body 20 forward
toward the inlet section (e.g., into the inlet flow). Preferably,
the center member 43 includes a faired forward end with a
hydrodynamic fairing to allow smooth flow over and around the
center member 43 and central body 20 and into the impeller blades
28.
[0075] FIG. 6A shows four inlet flow conditioning vanes 40 having a
cantilever type design wherein the inlet flow conditioning vanes 40
extend inward from the inside circumference of the outer casing 10
along a radial line extending generally radially to a center member
43 at the longitudinal centerline axis 2.
[0076] FIG. 6B shows exemplary inlet flow conditioning vanes 40
that are leaned in a circumferential direction to provide an
acoustic benefit. As shown in FIG. 6B, four inlet flow conditioning
vanes 40 extending inward from the inside circumference of the
outer casing 10 to a center member 43 and the individual inlet
vanes 40 are leaned in the circumferential direction.
[0077] The center member 43 may be an independent structure free of
the center body 20, or, preferably, the center member 43 is
connected to the center body 20. As shown in FIG. 5, the center
member 43 is stationary and a shaft (not shown) extends between the
center body 20 and the center member 43 and supports the rotating
impeller 21. Bearings (not shown) can be located at the forward end
and after end of the pump impeller 21 to allow the impeller 21 to
rotate. This embodiment having a center member 43 provides
additional structural support for the outer casing 10, center body
20, and impeller 21. A mixed flow pump system 1 having a center
member 43 makes the mixed flow pump system 1 more rugged and
resistant to shock and vibration.
[0078] FIGS. 1 and 5 show curved inlet flow conditioning vanes 40.
As shown in FIGS. 1 and 5, the inlet flow conditioning vanes 40 are
generally shaped as a foil or wing, but other shapes may be used
depending on the particular application. In one embodiment shown in
FIG. 1, the inlet flow conditioning vanes 40 can be oriented to
curve or turn in the same direction as the direction of impeller 21
rotation, which reduces the relative velocity thereby reducing
cavitation.
[0079] In another embodiment shown in FIG. 5, the inlet flow
conditioning vanes 40 can be oriented to curve or turn into the
direction of impeller 21 rotation, which results in increasing the
relative velocity of the fluid flow enter the pump impeller 21 and
increasing the head rise potential of the pump.
[0080] In yet another embodiment shown in FIG. 3, the inlet flow
conditioning vanes 40 can be straight vanes having a span (e.g.,
length) that is aligned with the longitudinal centerline 2, which
tends to take distortions out of the inlet flow.
[0081] The shape, number, size and exact position of the inlet flow
conditioning vanes 40 can be varied to optimize these parameters
and achieve the desired flow conditioning for the particular
application. The vanes may span a portion of the duct as shown in
FIG. 1 and 3, or the entire duct, as shown in the center member 43
arrangement of FIG. 5. For example, the shape, number, size, and
position of the inlet flow conditioning vanes may be determined by
the degree of swirl required to reduce the relative flow velocity
at the impeller eye and thereby reduce cavitation and noise.
Alternatively, the shape, number, size, and position of the inlet
flow conditioning vanes may be determined to increase the relative
flow velocity of the fluid flow entering the impeller thereby
improving the head of the pump.
[0082] Central Body
[0083] As shown in the Figures, the mixed flow pump system 1
includes a central body 20 disposed within the outer casing 10 and
that is coincident with the centerline axis 2 or axis of rotation
of the pump impeller 21. The central body 20 is align along and
extends axially along the longitudinal centerline axis 2 of the
pump outer casing 10 from the impeller section 12 and into the
outlet section 13.
[0084] The central body 20 includes a stationary portion and the
rotating rotor or mixed flow pump impeller 21. The central body 20
may include a solid body or a hollow shell body. Preferably, the
central body 20 includes a faired forward end 30, as part of the
rotating impeller 21, a generally cylindrical mid-section 31 and a
faired after end 32, as part of the stationary portion, to allow
smooth flow over and around the central body 20.
[0085] The central body 20 has a smaller cross-sectional area than
the outer casing 10 and is disposed within the outer casing 10.
Annular flow passage 6d is defined between the outer casing 10 and
the central body 20. Preferably, the shape of the central body 20
corresponds to the shape of the outer casing 10.
[0086] Impeller Section
[0087] The impeller section 12 is disposed between and connects the
inlet section 11 and the outlet section 13. As shown in the
Figures, the impeller section 12 includes a mixed flow pump 3
having a pump impeller 21 rotatably connected to the central body
20. The mixed flow pump impeller 21 is used to increase the energy
of the fluid flow contained internal to the outer casing 10. The
mixed flow pump 3 is used to draw a fluid from one of an internal
and an external fluid environment into the inlet of the mixed flow
pump system 1. The mixed flow pump 3 is used as a means of adding
hydraulic energy to the fluid in order to generate thrust.
[0088] The mixed flow pump impeller 21 includes a hub 27, blades
28, and flow passageways 29. The inlet of the pump is preferably
designed to receive a flow of fluid and preferably includes a
fairing 30 at the impeller hub to allow smooth flow entry into the
impeller blades 28 and passages 29. The hub 27 holds the impeller
blades 28 in place and rotates as an assembly connected by a shaft
(not shown) to a drive source 50, such as an electric motor or
other motive device.
[0089] Referring to FIG. 1, the impeller 21 can be rotating in a
counter clockwise direction looking aft from the forward end or
inlet end of the mixed flow pump impeller (e.g. in the direction of
arrow 35). As shown, the impeller 21 includes four impeller blades
28 and the impeller blades 28 are turned into the same direction as
the rotor rotation (e.g., the closest side rotates upward in the
counter clockwise direction). Accordingly, the blades 28 are
turning the flow in the same direction as rotor rotation (arrow
35).
[0090] The impeller 21 rotates within the impeller sweep. The
impeller sweep is defined by the span (e.g., longitudinal length)
of the impeller blades 28. The impeller rotation is causing the
flow to rotate in the same direction as the direction of rotation
of the impeller 21. The stator vanes 45, which are located down
stream of the impeller 21, are removing that swirl from the exiting
flow and causing the flow to turn back to the parallel or axial
orientation again (e.g., parallel to the centerline axis 2).
[0091] The mixed flow pump impeller 21 rotates within the outer
casing 10. The term "mixed flow" is meant to include its common
meaning in the art that the impellers are neither pure radial
impellers nor pure axial impellers. The increased energy provided
by the mixed flow pump 3 results in higher pressure in the flow,
resulting in thrust being produced as the flow exits the
propulsor.
[0092] The mixed flow pump 3 preferably covers the entire range
between a pure radial pump and a pure axial pump. In other words,
mixed flow preferably lies on a continuum between, but not
including, 100% radial to 100% axial. The mixed flow pump 3 exists
in a range between pumps considered axial and pumps considered
radial. For example, a pump is radial if the axial velocity at the
discharge is zero. If there is any positive radial flow at the
discharge, then the pump is a mixed flow pump.
[0093] Mixed flow pumps allow for a lower internal velocity
propulsor and consequently improved cavitation and acoustic
performance. Also, mixed flow pumps do not break down in cavitation
and therefore, even through the wetted surfaces of the mixed flow
pump system 1 may be greater than a convention external propulsor,
the internal mixed flow pump system 1 of the present invention has
a higher efficiency over the whole range of impeller devices.
[0094] For example, while cavitation issues may limit the
achievable speed of conventional external propulsors (e.g.,
cavitation won't produce thrust), a vehicle having an internal
mixed flow pump system 1 of the present invention can achieve
higher speeds because cavitation is not an issue. Also, a vehicle
having an internal mixed flow pump system 1 can not only achieve
higher speeds than conventional propulsors, but can achieve higher
speeds without making additional noise or vibration.
[0095] As shown in FIGS. 7A, 7B, and 7C, the pump impeller 21 may
include an open, a shrouded, or an embedded shroud design. FIG. 7A
shows a pump impeller 21 having an open blade construction. As
shown in FIG. 7A, with an open blade pump the impeller blades
extend outward from the hub 27 of the impeller 21 and a gap 33
exists between the tips 34 (e.g., distal ends) of the blades 28 and
the outer casing 10. In each of these configurations, a small
clearance gap 33 exists between the tip 34 of the rotating impeller
blades 28 and the outer casing 10.
[0096] FIG. 7B shows a shrouded impeller blade design. As shown in
FIG. 7B, a shroud 36 may be attached to the tips 34 of the impeller
blades 28 to provide additional flow conditioning, structural
support, and/or cavitation resistance. The shroud 36 at the tip 34
of each blade 28 is connected to and rotates with the impeller
blade 28. Again, a small gap 33 exists between the tip 34 of the
rotating impeller blades 28 and the outer casing 10.
[0097] In addition, the mixed flow pump 3 may include an embedded
shroud (or trenched shroud) design as shown in FIG. 7C. As shown in
FIG. 7C, the shroud 36 may be recessed into a groove 37 in the
outer casing 10 in order to maintain a smooth flow surface
connecting the outer casing 10 and the inside surface of the shroud
36. Preferably, the inside surface of the outer casing and the
inside surface of the shroud form a substantially continuous or
smooth surface, except for the small gap 33a between the groove 37
and the shroud 36. Since this small gap 33a is so small and is
oriented perpendicular to the direction of fluid flow, the flow
substantially jumps over the small gap 33a.
[0098] Stator Vane Assembly
[0099] The mixed flow pump system 1 includes a stator vane assembly
disposed in the outlet section 13 downstream of the mixed flow pump
3. The stator blade assembly includes a plurality of individual,
stationary stator blades 45 that are connected at one end to the
outer casing 10 and connected at the other end to the central body
20. The stator blades 45 provide structural support for the central
body 20 within the outer casing 10. Preferably, the stator blades
45 extend radially between the outer casing 10 and the central body
20 to provide flow conditioning of the fluid flow exiting the
rotating impeller 21 convert rotational energy imparted to the
fluid flow by the impeller blades into axial flow energy after the
stator vanes 45.
[0100] As shown in FIGS. 1 and 5, the stator blades 45 preferably
include shaped blades to remove swirl imparted to the flow by the
mixed flow pump impeller 21. This feature operates to convert the
kinetic energy contained within the swirl velocity to pressure
which is then available as thrust from the mixed flow pump system
1. Optimum performance is achieved when all flow swirl velocity is
removed from the fluid flow. Preferably, the stator vanes 45 are
hydrodynamically matched to the mixed flow pump impeller 21 to
maximize the removal of swirl velocity from the flow exiting the
impeller 21.
[0101] Preferably, the stator blades 45 are generally foil or
airfoil shaped blades, however their exact shape, size, position
and number can vary. As shown, the stator vanes include a first or
forward end 46 and a second or aft end 47 located downstream of the
forward end 46. As shown, the stator vanes 45 can include a greater
thickness at the first end 46 and may taper down to a smaller
thickness at the second end 47.
[0102] The stator blades 45 are preferably evenly spaced around the
circumference of the inside of the outer casing 10 and the outside
of the central body 20. The span of the stator vanes 45 is
determined based on the desired flow conditioning (e.g., the span
of the stator vanes 45 may be related to the degree of swirl they
must remove from the flow exiting the impeller 21 to ensure a
smooth discharge flow).
[0103] Outlet Section
[0104] As shown in FIG. 1, the outlet section 13 includes outlet
ducting 24 for containing and guiding a flow of fluid from a first
end of the outlet ducting 24 at the pump outlet 6c of the mixed
flow pump 3 through the outlet section 13 to a second end of the
outlet ducting 24 at the system outlet opening 4b. The outlet
ducting 24 includes the annular axial discharge passage 6d between
the outer casing 10 and the first portion 8a of the central body
20, a transition section proximate the second portion 8b of the
central body 20 where the outer casing 10 converges and the central
body 20 fairs down to a nozzle 25.
[0105] Preferably, the outlet ducting 24 has a generally circular
cross-section, although other shapes may be suitable. In addition,
the outlet ducting 24 preferably includes a generally decreasing
cross-sectional area from the first end to the second end for
causing an acceleration of the fluid flow passing there
through.
[0106] In embodiments having outlet ducting 24 having a generally
decreasing cross-section, flow may be accelerated by progressively
decreasing the flow area to increase the flow velocity, thereby
providing a high velocity fluid flow to produce thrust. This can be
accomplished, for example, by gradually decreasing the diameter of,
for example, a circular shaped outer casing 10 over the length of
the outlet section 13.
[0107] Discharge Nozzle
[0108] As shown in FIG. 1, the mixed flow pump system 1 can include
a discharge nozzle 25 located proximate the system outlet opening
4b for discharging the high-energy fluid flow from the mixed flow
pump system 1 to produce thrust.
[0109] Thrust is produced by the acceleration of the flow from the
mixed flow pump impeller 21 and in the discharge nozzle 25. High
pressure in the flow is converted to velocity in a flow jet, with
the change in linear momentum being related to the net thrust
produced. The discharge of the nozzle 25 may be circular,
elliptical, rectangular, or other shapes as required, to interface
with a particular application in an optimum manner.
[0110] In addition, a thrust vectoring mechanism 60 can be used to
direct the thrust in the desired direction. This can be
accomplished by vectoring the discharge nozzle 25, vectoring a pod
or module housing the mixed flow pump system 1, and the like.
[0111] Preferably, smooth flow is maintained from the discharge of
the stator assembly to the discharge nozzle 25 of the mixed flow
pump system 1. In addition, it is preferred that the shape of the
outer casing 10 and the shape of the central body 20 are such that
constant area or a smooth variation in flow area is maintained
throughout the internal flow passage 6a-6e. To this end, the mixed
flow pump system 1 preferably includes one or more fairings at a
forward end of the central body 20 (e.g., at the impeller 21), a
forward end of the center member 43, and the after end of the
central body 20 in order to facilitate smooth flow through the
internal flow passage 6a-6e and over/around the central body
20.
[0112] Drive Source
[0113] The mixed flow pump system 1 includes a drive source 50 for
driving the mixed flow pump 3 and causing the pump impeller 21 to
rotate and impart energy to the fluid flowing through the mixed
flow pump system 1. The drive source can include a motor 50 that
provides a driving force to rotate the mixed flow pump impeller 21.
In a preferred embodiment shown in FIGS. 1 and 8, the motor 50 is
aligned along the longitudinal centerline axis 2 of the mixed flow
pump system aft of the mixed flow pump 3 and in the flow
stream.
[0114] In an embodiment having the drive source 50 positioned
internal to the fluid flow, the drive source 50 can be housed in
the central body 20 and electrical power lines (not shown) to the
motor may extend through one of the stator vanes 45. In a preferred
embodiment, the motor 50 includes a high energy density motor.
[0115] In an alternative embodiment (not shown), the motor 50 may
be located external to flow stream. For example, the motor 50 may
be located on the exterior of the outer casing 10 and a drive shaft
and gears, such as a right angle drive and a set of beveled gears,
can be used to connect the output shaft of the motor 50 to the
input shaft of the mixed flow pump impeller 21. In another
embodiment (not shown), the drive source could include a rim drive
motor. For example, a rim drive motor could be attached to the
shroud or embedded shroud and exist outside the outer casing.
Bearings in the central body 20 fairing could be provided to
support the rotor in the rim driven assembly.
[0116] Operation
[0117] The design and operation of the mixed flow pump system 1 can
also be described in terms of the flow of liquid through an
exemplary system, such as the exemplary mixed flow system 1 of FIG.
1. In one exemplary system, the flow begins at the system inlet 4a
and flows in the inlet flow passage 6a through circular inlet
ducting 15. The flow then optionally conditioned as it passes
through the inlet flow conditioning vanes 40. Once past the inlet
flow conditioning vanes 40, or concurrently therewith, the diameter
of the inlet ducting 15 preferably increases gradually.
[0118] The fluid flow enters the pump impeller 21 through the pump
inlet 6b and passes through the impeller passageways 29 and exits
out of the pump outlet 6c.
[0119] The flow becomes annular as the flow exits the impeller
passageways 29 and enters the annular flow passage 6d of the outlet
ducting 24, which, in this exemplary embodiment, also has a
circular cross section. The flow continues in an annular manner
around the motor/impeller housing (e.g., the central body 20) to a
maximum cross section diameter for the pump casing 10 and then flow
continues aft through the annular flow passage 6d while the
circular cross section of the outlet duct 24 preferably decreases
in diameter gradually.
[0120] Prior to entering a transition area, and typically near the
maximum cross section diameter, the flow passes through foil-like
blades or stator vanes 45 that eliminate tangential flow (swirl)
and provide support for the motor/impeller housing 20. Flow then
transitions from the annular flow back to a flow of circular cross
section as the flow passes the end of the motor/impeller housing 20
and into the outlet flow passage 6e. Flow then exits the system
outlet 4b, preferably through an outlet nozzle 25, to provide
thrust.
[0121] In another exemplary embodiment, where the co-axial mixed
flow pump system 1 includes an axial forward looking inlet and is
operating in an external fluid environment, such as the exemplary
mixed flow pump system 1 of FIG. 8, the production of thrust can be
accomplished as follows: A quantity of flow enters the system inlet
4a at some velocity, nominally slightly lower than the speed of the
vehicle to which the mixed flow pump system 1 is installed. The
flow is diffused in the inlet to increase its pressure. In one
embodiment, some swirl may be added by inlet flow conditioning
vanes 40 to reduce the velocity of the flow as it enters the pump
impeller 21. The flow energy or pressure is increased in the
rotating pump impeller 21. Energy, for example, in the form of
torque and RPM on a motor shaft, is provided to accomplish this. As
the flow leaves the pump impeller 21, it exhibits a large value of
swirl velocity, nominally a large fraction of the rotational speed
of the pump impeller 21. This rotational velocity is removed and
converted to additional pressure rise in a set of stationary stator
vanes 45. The high pressure flow continues to a contracting nozzle
25 where this pressure is converted into velocity, which is
discharged from the nozzle 25 into the fluid surrounding the
vehicle, thereby propelling the vehicle through the fluid operating
environment.
[0122] The velocity of the discharged flow is nominally 1.5 to 3
times the velocity of the vehicle. The mass flow rate times the
change in the velocity of the flow from the inlet to the jet is
nominally equal to the thrust produced by the mixed flow pump
system 1. A vectoring mechanism 60 can be provided for moving the
nozzle 25 to produce vectored thrust in a desired direction.
[0123] Exemplary Applications
[0124] The invention has applications in a variety of marine
vehicles, including surface crafts, submerged crafts, weapons and
unmanned underwater vehicles (UUVs) of various sizes and speed
requirements. The propulsion modules may be used as single units or
in a distributed propulsion system where additional thrust and
enhanced maneuvering may be required. The modules exhibit superior
resistance to cavitation due to the use of low RPM mixed flow
impellers.
[0125] Potential Applications include: conventional surface ships
with displacement hulls; air-cushioned bodies (e.g., hover craft);
surface ships with strut mounted or pod-propulsors; submersible
ships and submarines with internal propulsors or external
pod-propulsors; weapons; autonomous/unmanned underwater vehicles;
mines; other small submerged vehicles with internal or
pod-propulsors; swimmer assist vehicles; maneuvering thrusters,
thrust vectored propulsors, harbor tugs; pleasure craft and
auxiliary/emergency propulsion; floating platform stabilizers;
non-marine hydraulic applications such as: irrigation, fire, water
handling and distribution, cooling system pumps, power generation
(pumped storage) systems; chemical distribution systems, slurry
handling flows, and wells fluid extraction; medical devices such as
heart assist pumps, drug infusion pumps, and dialysis pumps;
etc.
[0126] Advantages and New Features of Preferred Embodiments
[0127] The mixed flow pump provides several performance
enhancements in the areas of inlet flow conditioning, higher
pressure thrust propulsion, maneuvering, vibration control,
cavitation, and the like.
[0128] A significant advantage in cavitation performance and
acoustic performance can be achieved by reducing the relative
velocity of the fluid flow over the impeller blades. This can be
accomplished by use of inlet flow conditioning vanes and/or the use
of a low/reduced RPM motor. By reducing the relative velocity, by
using one or both of these techniques, the cavitation and vibration
noise can be reduced.
[0129] The use of a forward looking, axial inlet, as opposed to a
flush inlet, provides additional cavitation resistance due to
higher available pressure at the inlet to the pump impeller.
[0130] The use of flush inlets facilitates installation in some
applications with minimum loss of performance.
[0131] The use of stator vanes to remove flow swirl velocity
creates a condition of the unit having no external torque loads.
The use of stator vanes replaces the traditional use of a scroll
casing that can cause inefficiency at off-design operation and
blade rate tones in the cutoff region of the casing.
[0132] The availability of high energy density electric motors
makes a smaller diameter unit feasible, consequently, the
installation in some applications is facilitated. These high energy
density electric motors solves the packaging problems and also
allows for lower RPM motors to be used. This provides the advantage
of a lower volume and lower RPM resulting in a lower relative
velocity at the pump impeller and hence reduced cavitation and
vibration noise.
[0133] In embodiment employing a rim-type motor located in the
fluid flow, motor cooling water can be taken directly from
propulsion water stream.
[0134] The propulsor can be modular, making installation, repair,
and fabrication more economical and reducing downtime or shipyard
time wherein the system/ship is out of service for maintenance or
repairs.
[0135] The production of units of different size or power
capabilities makes implementing a distributed propulsion system
attractive. This concept increases availability and redundancy
compared to a single propulsion plant installation.
[0136] Thrust vectoring adds capability in terms of maneuvering and
sea-keeping, as well as other potential operating advantages, i.e.
small radius turns. A fly-by-wire method of controlling multiple
pumps in an application can provide ship stability and high
accuracy maneuvering without using conventional control
surfaces.
[0137] The mixed flow pump units can be installed either internal
to a hull or external in pods, or other submerged appendages.
[0138] While the invention has been particularly shown and
described with reference to preferred embodiments thereof, it will
be understood by those skilled in the art that various alterations
in form and detail may be made therein without departing from the
spirit and scope of the invention. In particular, the specific
shape and size of the mixed flow pump, the number and shape of the
inlet conditioning vanes, the impeller design, the angle at which
the fluid exits the mixed flow impeller from the shaft axis, the
specific number and shape of the stator blades, and the means for
producing vectored thrust can be altered depending on the specific
application without departing from the scope of the invention.
* * * * *